Imbibition: An Example of Nonconserved Cellular Automaton

We report an imbibition experiment in 2D random porous media in which height - height correlation function grows with a nonuniversal exponent. We find the exponent to depend on evaporation. A cellular automaton model for imbibition based on first principles is presented. A numerical study of the model gives results which are consistent with the experiment. The interface is shown to exhibit self-organised criticality (SOC).